Root Formation of Pea Cuttings in Relation to the Irradiance of the Stock Plants

Pea plants were grown at different irradiances for eleven days. At this stage they were used for cuttings. The irradiance during the rooting period (155 mW · dm^?2) was the same in all the experiments, Cuttings from stock plants cultivated at the weakest irradiance obtained the highest number of roots, and the poorest rooting appeared in cuttings from stock plants grown at the highest irradiance. The results indicate that the nutritional status of the stock plant is an important factor for root formation in the cutting. Light may influence the production of inhibitors which directly or indirectly affect root formation. The possible role of carbohydrates and growth promoters in the process of root formation is discussed.     

Adventitious Root Formation Induced by Gibberellic Acid and Regulated by the Irradiance to the Stock Plants

Pea plants (Pisum sativum L. cv. Alaska) were grown from seeds for eleven days at different irradiances. Cuttings were then excised and rooted at 16 W × m^?2. Gibberellic acid (GA₃, 10^?11 to 10^?3M) was applied to the cuttings immediately after excision. Cuttings from stock plants grown at the highest level of irradiance (38 W × m^?2) formed the lowest number of roots. An increasing number of roots per cutting was obtained by decreasing the irradiance to the stock plants. In cuttings from stock plants grown at low irradiances, low concentrations of GA₃ (10^?8 and 10^?7M) promoted root formation further. No effect on rooting by these GA₃ concentrations was observed when applied to cuttings originating from stock plants grown at the high irradiances. Root formation in all cuttings was inhibited by GA₃ at concentrations higher than 10^?6M. The degree of inhibition by GA₃ was influenced by the irradiance pretreatment and was increased with an increase in the irradiance during the stock plant growth. Seeds from different years produced cuttings with different response patterns regarding the irradiance and GA₃ effects on rooting.     

Influence of the Irradiance on Carbohydrate Content and Rooting of Cuttings of Pine Seedlings (Pinus sylvestris L.)

Seedlings of Pinus sylvestris L. were grown for 6 weeks at an irradiance of either 8 or 40 watts per square meter in a controlled environment room. Cuttings from these plants were rooted in tap water for 75 days at either 8 or 40 watts per square meter. The photoperiod was 17 hours.

During the first 30 days of the rooting period quantitative changes in carbohydrates were recorded in cuttings from the different treatments. The carbohydrate contents of the cuttings were mainly regulated by the irradiance during the stock plant stage and generally a higher carbohydrate level was found in cuttings from stock plants grown at 40 watts per square meter.

The irradiance during the rooting period had only minor effects on the time course of root formation, whereas the irradiance during the stock plant stage did influence the subsequent root formation. Cuttings from stock plants grown at 8 watts per square meter rooted faster and with higher frequency than those from stock plants grown at 40 watts per square meter. These results are discussed in relation to the mentioned irradiance effects on carbohydrate content.

     

Influence of Cotyledon Excision and Sucrose on Root Formation in Pea Cuttings

Sucrose was supplied to stock plants of Pisum sativum L. cv. Alaska grown at different levels of irradiance. There was no significant effect on the rooting of the cuttings by sucrose supply to intact plants regardless of the irradiance. However, an increase in the number of roots per cutting was obtained at increasing concentrations of sucrose when the stock plants had been grown at 4 W m^?2 and their cotyledons had been removed two days before the cuttings were excised. Cotyledons were removed from stock plants at different times before the excision of cuttings with the intent to regulate the endogenous supply of carbohydrate. The number of roots per cutting was reduced by removal of the cotyledons and this reduction was correlated to the number of days the stock plants had grown without cotyledons as well as to the irradiance pre-treatment. A greater reduction occurred in cuttings from plants grown under 4 W m^?2 than from those grown under 38 W m^?2. The growth of the stock plants and the subsequent stem growth of the cuttings was determined by the irradiance to the stock plants and by the time of removal of the cotyledons. Exogenous supply of sucrose had no effect on the stem growth of the cuttings.     

Effects of auxin and irradiance on the rooting of cuttings of Pinus sylvestris

Abstract Seedlings of Pinus sylvestris L. were grown under controlled conditions (temperature 20°C, photoperiod 17 h) at two irradiances, 8 or 40 W m^-2. Hypocotyl cuttings were excised and rooted at different irradiances in tap water solutions of indolebutyric acid (IBA). The fastest rooting and highest rooting percentage were obtained with cuttings from stock plants grown at 8 W m^-2 and treated with 10^-5M IBA for 21 days. The concentration of 10^-4M IBA inhibited root formation. In comparable treatments rooting was always better in cuttings from stock plants grown at 8 W m^-2 than in cuttings from stock plants grown at 40 W m^-2. The irradiance during the rooting period had only a minor influence on rooting. When cuttings from plants irradiated with 40 W m^-2 were treated with 10^-5M IBA for 21 days the rooting percentage almost reached the same level as in untreated cuttings from stock plants given 8 W m^-2. In cuttings treated with IBA during the whole rooting period, rooting was depressed in comparison to untreated cuttings. Aeration of the 10^-4M IBA solution increased the rooting percentage, but aeration had no effect on untreated cuttings and on cuttings treated with lower IBA concentrations.     

Quantification of IAA Metabolites in the Early Stages of Adventitious Rooting Might Be Predictive for Subsequent Differences in Rooting Response

Stock mother plants have gained importance in the process of adventitious rooting of woody plants in recent years. The present study reveals the role of the cutting position from a stock mother plant for subsequent rooting. Cuttings of Prunus subhirtella Miq. var. Autumnalis which originated from suckers at the bottom of a tree developed a rooting system of better quality (rooted cutting without callus formation, more main roots) compared to cuttings which originated from shoots at the top of a tree. The latter accumulated significantly more indole-3-acetic acid (IAA) with the highest value of 25.37 μg g^?1 FW on the severance date. These cuttings also contained more indole-3-acetyl-aspartate (IAA-Asp) on the second day after severance with the highest value of 4875.95 μg g^?1 FW compared to cuttings from the bottom-deriving suckers. The latter metabolised IAA primarily via 2-oxindole-3-acetic acid (oxIAA) and indole-3-methanol because the concentrations of these compounds increased at the base of these cuttings. The highest concentration of oxIAA, 8.3 mg ekv. IAA g^?1 FW, was measured 1 h after severance in cuttings from the bottom-derived suckers. With 590.5 ng ekv IAAg^?1 FW, the indole-3-methanol values were also significantly higher in the cuttings from the bottom shoots compared with cuttings from the top of the tree.     

The lose of juvenility elicits adventitious rooting recalcitrance in apple rootstocks

For perennial woody plants, softwood cutting is an efficient technique for larger scale propagation and adventitious rooting of cuttings is one of the most crucial steps. To evaluate the significance of juvenility on adventitious rooting, rooting rates was compared between softwood cuttings collected from apomictic seedlings (juvenile), in vitro cultured plants (rejuvenated), suckers (juvenile like) and canopy shoots (adult) of reproductively mature trees in Malus xiaojinensis. After pre-treatment with indole-3-butytric acid (IBA) (3,000 mg L^?1) + H₂O₂ (50 mM), rooting rates in cutting from juvenile, juvenile like and rejuvenated donor plants were significantly higher (>90 %) than that from adult trees. The effects of IBA on adventitious rooting were enhanced significantly by exogenous H₂O₂. After 15 passages of in vitro subculture, the micro-shoots from adult phase explants were rejuvenated successfully, marked by the elevated expression of miR156 in the leaflets of the micro-shoots. But the rooting ability of rejuvenated micro-shoots was recovered delayed at the 18th or 21st passage of subculture. During the process of rejuvenation, the leaf indole-3-acetic acid contents and the expressions of rooting related genes CKI1, ARRO-1, ARF7 and ARF19 increased significantly. In contrary, the leaf abscisic acid contents decreased. A lack of juvenility is the most important limiting factor governing adventitious rooting of softwood cuttings in apple rootstocks.     

Light effects on root formation in aspen and willow cuttings

The effect of light on rooting of leafy cuttings of aspen (Populus tremula × tremuloides) and a willow hybrid (Salix caprea × viminalis) was investigated under controlled conditions in water culture. Two levels of irradiance were used, 40 and 8 W m^?2. The lower level gave the best rooting of aspen cuttings, both when applied to the stock plants before the cuttings were taken and when given to the cuttings during the rooting period. Irradiation of the cutting base during the rooting period inhibited rooting almost completely in aspen and decreased the number of roots formed in the Salix hybrid. Net photosynthesis in the cuttings of Salix decreased considerably after excision and increased again after formation of roots. Indirect evidence indicated that photosynthesis was even more affected in aspen cuttings. The possible roles of carbohydrates and inhibitors in the light effects are discussed.     

A relationship between irradiation, carbohydrates and rooting in cuttings of Pisum sativum

Rooting ability was studied for cuttings derived from pea plants ( Pisum sativum , L. cv. Alaska) grown in controlled environment rooms. When the cuttings were rooted at 70 μmol m⁻² s⁻, ¹ (photosynthetic photon flux density) or more, a stock plant irradiance at 100 μmol m⁻² s⁻¹ decreased rooting ability in cuttings compared to 5 μmol m⁻², s⁻¹, However, cuttings rooted at 160 μmol m⁻² s⁻¹ formed more roots compared to 5 (μmol m⁻² s⁻¹. Although a high irradiance increased the number of roots formed, it could not overcome a decreased potential for root formation in stock plants grown at high irradiance. Light compensation point and dark respiration of cuttings decreased by 70% during the rooting period, and the final levels were strongly influenced by the irradiance to the cuttings. Respiratory O₂ uptake decreased in the apex and the base of the cutting from day 2 onwards, whereas a constant level was found in the leaves. Only the content of extractable fructose, glucose, sucrose and starch varied during the early part of the rooting period. We conclude that the observed changes in the cuttings are initiated by excision of the root system, and are not involved in the initiation of adventitious roots.     

Physiological adaptations of five poplar genotypes grown under SRC in the semi-arid Mediterranean environment

Key message

The genotype ‘Neva’ under high plant density showed the highest biomass yield and optimal physiological strategies and could be the most suitable choice under semi-arid environment

Abstract

The poplars (Populus spp.) are the most sensitive plants to water deficit conditions among the woody species utilized for biomass production for energetic purposes; their productivity is associated with water availability in the soil. In the Mediterranean environment, crops are mainly limited by evapotranspirative demand that is not balanced by rainfall supply. As new hybrids with high growth rates and resistance to water stress are selected, the use of poplar as an energy crop may increase in Southern regions of Mediterranean Europe. The growth dynamics and physiological characteristics of poplar hybrid genotypes have been monitored for 2 years at a site with a Mediterranean climate, Apulia region, that could be used for energy crops. Unrooted cuttings of three recently selected genotypes of poplar (‘Neva’, ‘Dvina’ and ‘Lena’) and two “traditional” genotypes (‘Luisa Avanzo’ and ‘Bellini’) were planted in the spring of 2010 at two different densities: (a) low plant density = 1,667 cuttings ha^?1 (LPD); (b) high plant density = 6,667 cuttings ha^?1 (HPD). The genotypes ‘Lena’ and ‘Dvina’ showed the lowest survival rates and the poorest growth among the hybrid poplar tested. The genotype ‘Bellini’ had low stomatal sensitivity to soil water content and a moderate productive performance. The genotypes ‘Luisa Avanzo’ and ‘Neva’ had a good degree of rooting and sprouting, high values of leaf relative water content (RWC_l) and low values of stomatal conductance (g _s) during the summer months. In “Neva”, these characteristics were associated with the best yields (4 t ha^?1) in HPD.     

Aeroponics for adventitious rhizogenesis in evergreen haloxeric tree <Emphasis Type="Italic">Tamarix aphylla</Emphasis> (L.) Karst.: influence of exogenous auxins and cutting type

Tamarix aphylla (L.) Karst., a drought resistant halophyte tree, is an agroforestry species which can be used for reclamation of waterlogged saline and marginal lands. Due to very low seed viability and unsuitable conditions for seed germination, the tree is becoming rare in Indian Thar desert. Present study concerns the evaluation of aeroponics technique for vegetative propagation of T. aphylla. Effect of various exogenous auxins (indole-3-acetic acid, indole-3-butyric acid, naphthalene acetic acid) at different concentrations (0.0, 1.0, 2.0, 3.0, 5.0, 10.0 mg l^?1) was examined for induction of adventitious rooting and other morphological features. Among all three auxins tested individually, maximum rooting response (79%) was observed with IBA 2.0 mg l^?1. However, stem cuttings treated with a combination of auxins (2.0 mg l^?1 IBA and 1.0 mg l^?1 IAA) for 15 min resulted in 87% of rooting response. Among three types of stem cuttings (apical shoot, newly sprouted cuttings, mature stem cuttings), maximum rooting (~ 90%) was observed on mature stem cuttings. Number of roots and root length were significantly higher in aeroponically rooted stem cuttings as compared to stem cuttings rooted in soil conditions. Successfully rooted and sprouted plants were transferred to polybags with 95% survival rate. This is the first report on aeroponic culture of Tamarix aphylla which can be utilized in agroforestry practices, marginal land reclamation and physiological studies.     

A Relationship between Length of Basis and Adventitious Root Formation in Pea Cuttings

A positive correlation between the length of the basis and the ability of the cuttings to form adventitious roots was observed in pea cuttings. Plants with a different basis length (the third internode) were obtained in different ways: Regulation by the level of irradiance, dark treatment or gibberellic acid. The length of the basis was also regulated by excision of the cuttings at different places on the stock plants. With increasing basis length an increase was found in the number of roots subsequently formed. The results were similar in cuttings from plants grown at different levels of irradiance or from dark treated plants. Optimal rooting was obtained by cutting the plants just above the second scale leaf. Cuttings from plants treated with 10^?3M GA₃ showed the same correlation between the length of the third internode and root formation as found in the other experiments, but the number of roots were at a lower level.     

Reproductive biology of the invasive Asian freshwater leech Barbronia weberi (Blanchard, 1897)

Barbronia weberi were collected from Hydrilla verticillata purchased from aquarium suppliers in Melbourne, Australia and additional B. weberi were obtained from aquatic plants in Canberra, ACT, Australia. Adult leeches fed Tubifex sp. ad libitum successfully reproduced under laboratory conditions (21 ± 5?°C ). Reproductively mature B. weberi produced cocoons every week for up to three months at which time the adults began to senesce. Cocoons contained one to five (barx=2.41±0.78 SD, N=58) eggs with juveniles leaving the cocoon within 27 ± 3.4 SD days (N=13) of cocoon production. Juvenile B. weberi reached reproductive maturity within four months (N=7) of hatching and had a maximum growth rate of 1.10 mm² d^?1 once they left the cocoon at around 30 days. Individual egg volume (r=0.63, scaling exponent = 1.21) and cocoon volume (r=0.65, scaling exponent = 1.24) showed a significant (P<0.001) and nearly isometric relationship when scaled with maternal body size. Because this species can grow rapidly and produce a large number of eggs over a short period of time and can piggyback with plant species and travel through the aquarium trade, there is potential for B. weberi to rapidly invade new localities.     

Seasonal changes in adventitious root formation in hypocotyl cuttings of Pinus sylvestris: Influence of Photoperiod during stock plant growth and of indolebutyric acid treatment of cuttings

Seedlings of Pinus sylvestris were grown for 6 weeks under natural light conditions in a temperature controlled environment room. Cuttings from these plants were rooted in tap water or in indolebutyric acid (IBA) solutions for 60 days at an irradiance of 16 W m^-2. Experiments were performed at 3-week intervals during two growth seasons. — Seasonal changes in root formation were found in control cuttings as well as in IBA treated cuttings. The number of roots and the percentage of cuttings that rooted were high during early spring and autumn. During the summer period hardly any roots were formed. Stimulation of root formation by IBA occurred manily during spring and autumn when cuttings already possessed the ability to form roots. — The influence of photoperiod during stock plant growth was also investigated. Shorter photoperiod resulted in an increase in the number of roots and rooting percentage. The period during summer where rooting was inhibited under natural light conditions was considerably shortened when stock plants were grown at a photoperiod of only 4 h. The results demonstrate the importance of the growing conditions for stock plants for subsequent root formation. The results are discussed with special reference to the role of irradiance.     

Morphactin and Adventitious Root Formation in Pea Cuttings

Stock plants of pea (Pisum sativum L. cv. Alaska) were grown at different controlled levels of irradiance (4, 16 or 38 W m^?2) for 11 days from sowing. Morphactin (CFM, methyl-2-chloro-9-hydroxy-fluorene-9-carboxylate) was applied to the apex of the stock plants 3 days before cuttings were excised. The cuttings were rooted at 16 W m^?2. High levels of morphactin (>5 × 10^?3 mg l^?1) inhibited root formation in the cuttings. Low concentrations of CFM (5 × 10^?5 mg l^?1) promoted the formation of adventitious roots in cuttings from plants grown at all three levels of irradiance, with the most pronounced effect in cuttings from 4 W m^?2. Measurements of ethylene evolution by CFM-treated plants 3 days after application, revealed a stimulatory effect on ethylene production by high CFM concentrations.     

Water stress and root formation in pea cuttings

The stock plants of pea (Pistum sativium L. cv. Alaska) grown for 11 days at 16 W m^?2 38 W m^?2 were subjected to different degrees of moisture stress, simulated with polyethyleneglycol (PEG, 6000) for different periods. The cuttings were made at the end of stress treatments, planted in perlite and allowed to root in a mist propagation chamber. The number of adventitious roots formed on the cuttings from non-stressed plants was significantly higher under low (16 W m^?2) than under high (38 W ^m?2) irradiance. However, under the influence of short duration stress the number of roots increased significantly under high but not under low irradiance. There was significantly poor rooting after prolonged stress under both irradiances. The leaf osmotic potential ψ_π showed a greater reduction with increasing degree and duration of stress at 38 W m^?2 than at 16 W m^?2. The differential rooting behaviour as a result of stress levels and irradiances is discussed in the light of available literature on adventitious root formation.     

The effect of indole-3-acetylaspartic acid on adventitious root formation on bean cuttings

The influence of indole-3-acetylaspartic acid (IAAsp) on rooting of stem cuttings from bean plants (Phaseolus vulgaris L.) of different ages, cultivated at different temperatures (17°, 21° and 25°C) was studied and compared to that of indole-3-acetic acid (IAA). At a concentration of 10^–4 M, IAAsp only nonsignificantly stimulated adventitious root formation, approximately to the same level as IAA in all treatments. IAAsp at 5×10^–4 M further enhanced rooting, by up 200% of control values, with little influence of temperature conditions and stock plant age. This concentration of IAA usually stimulated rooting more than the conjugate. The largest differences between the effects of IAAsp and IAA occured at the highest cultivation temperature of 25°C where stock plant age also influenced the response. The number of roots produced in comparison with the control, was enhanced from 350% on cuttings from the youngest plants to more than 600% on cuttings from the oldest. In contrast to the conjugate, 5×10^–4 M IAA induced hypocotyl swelling and injury of the epidermis at the base of cuttings, in all treatments.     

The effect of etiolation and shading of stock plants on rhizogenesis in stem cuttings of <Emphasis Type="Italic">Cotinus coggygria</Emphasis>

In order to improve vegetative propagation of a difficult to root Cotinus coggygria the stock plants were subjected to: etiolation, shading and spraying with IBA, combined with the application of two commercially available rooting powders. The IBA treatment was more suitable for rooting of C. coggygria cuttings than the NAA application and it enhanced rhizogenesis regardless of the form of auxin application (foliar application to a stock plant or a rooting powder used directly on cuttings) and the amount of light provided to stock plants. Etiolation did not improve rhizogenesis in stem cuttings, however, reduction of light intensity by 50% and 96% of the ambient prior to harvest of cuttings affected rooting positively. Positive effects of shading can be ascribed to changes in shoot anatomy, i.e. a weaker sclerenchyma development. Synergistic effect of shading and foliar auxin application can result from the increase in leaf blade area and/or thinner lower epiderm. Enhanced rooting in cuttings from shoots grown out under reduced light intensity was accompanied by decrease in the contents of total soluble sugars, soluble proteins and free ABA and by increase in total chlorophyll, free amino acids, polyphenolic acids and free IAA contents.     

A reliable methodology for assessing the in vitro photosynthetic competence of two Brazilian savanna species: Hyptis marrubioides and Hancornia speciosa

Evaluation of photosynthetic efficiency is critical for studies on plant responses to environmental conditions as well as for genotype selection; however, there is a lack of reliable and functional protocols for such assessments of plants cultured in vitro. In this study, we aimed to adapt the conventional methodology for measuring gas exchange of plants grown in vitro to analyze the effects of irradiance, flow rate, and air humidity on the photosynthetic rate in cultured plantlets of two ‘Cerrado’ species, namely Hyptis marrubioides and Hancornia speciosa plantlets. Chlorophyll (chl) a fluorescence and chloroplastidic pigment content were also assessed. The highest photosynthetic rates were observed at a photon flux density of 600 μmol m^?2 s^?1, with tube inlet airflow rates between 100 and 300 mL min^?1 and 80 % relative humidity in the inlet air. The electron transport rate curve, by means of chl a fluorescence, was similar to the photosynthetic rate response curve obtained with the infrared gas analyzer. These results demonstrate that both H. marrubioides and H. speciosa seedlings grown in vitro have a functional photosynthetic apparatus and respond to variations in measurement conditions, exhibiting substantial rates of CO₂ assimilation under saturating irradiance conditions. The methodology proposed here can be adapted and applied to other species growing in vitro.     

Pre and post-severance effects of light quality on carbohydrate dynamics and microcutting adventitious rooting of two Eucalyptus species of contrasting recalcitrance

Adventitious rooting is a complex developmental response affected by genetic and environmental factors. Radiation quality effects on adventitious rooting depend on characteristics such as species, growth stage, irradiance, spectral quality, and time of exposure. Eucalyptus is an essential genus for the paper industry, and high yield plantations depend on adventitious rooting of selected genotypes. This work addressed two hypotheses: (1) radiation quality equally affects adventitious rooting in Eucalyptus species of different recalcitrance; (2) adventitious rooting outcome depends on both donor plant and cutting radiation quality treatments. To that end, the easy-to-root Eucalyptus grandis and the recalcitrant Eucalyptus globulus were evaluated. The effect of white, blue, red and far-red radiation enrichment on microcuttings and donor plants of both species was evaluated in relation to rooting. There was no effect of radiation quality on adventitious rooting of E. grandis or when radiation treatments were applied to E. globulus microcuttings. In contrast, donor plants of E. globulus, grown in medium devoid of sucrose and exposed to far-red radiation, yielded microcuttings showing higher rooting percentage, even in the absence of exogenous auxin in the rooting medium. Sucrose in donor plant medium abolished the positive effect of far-red radiation. An increase in endogenous soluble sugars and starch contents in basal microcuttings was associated with far-red radiation treatment of donor plants. These results underline the importance of appropriate carbohydrate partitioning in donor plants for adventitious rooting of cuttings and provide a basis for understanding and overcoming rooting recalcitrance in E. globulus clones.